Characterization of water-participant hydrogen bonds in oil-paper insulation investigated with terahertz dielectric spectroscopy

In this study, aiming to characterize the dynamic polarization behavior of water molecules affected by hydrogen bonding with oil-paper insulation, we performed dielectric spectroscopy on oil-paper insulation with moisture contents of 0.4-4.7% in the terahertz band (0.3-3.3 THz). A relaxation-resonance integrated polarization model considering water-participant hydrogen bond (WHB) effects is established to describe the complex dielectric constant of oil-paper insulation with moisture. The theoretical model is in good agreement with the experimental results. By analyzing the relationship between the polarization parameters and moisture content, three states of WHBs are found. The WHB type, strength and disorder show different characteristics with increased moisture. Furthermore, molecular simulation studies are carried out, and the calculation results provided a persuasive argument for the analysis of terahertz dielectric spectroscopy. This research reveals an important new strategy for studying the polarization behavior of water molecules affected by oil-paper insulation as an experimental supplement to molecular simulation. The proposed test and analysis method render effective and sustainable progress in practical applications of rapid nondestructive evaluation and 2D imaging of moisture content distributed in oil-paper insulation.